PS and a warning:
The ssh tunnel failed permanently after a kernel upgrade and reboot. I have not investigated this further, but booting with the previous kernel (5.8.0-63) got it working again. The kernel that doesn’t work is 5.11.0-25. I suspect that something was changed in this kernel series that broke it and that future releases in the 5.11 series will also not work.
I am now placing a hold on kernel upgrades.
It looks like nobody has tried to follow this yet, else my error in this would have been spotted:
A parameter is missing. I’m going to correct that now.
Interesting question, but i dont belive that everyone who use VPN will get separate external IP with own subnet, so people will share trafik with other VPN users? More even if it free vpn.
I have struck another gotcha: when using ssh, portmap.io delete the port mapping every month. To keep it active, I have to log into their system and re-save the mapping. I asked them and apparently this does not happen with vpn connections, only with ssh.
For anyone doing port forwarding through a tunnel, how are you handling, or not, UDP to enable QUIC?
VPN providers usually allow you to have either TCP or UDP, to have both you need to create two rules to your connection, but for free accounts they usually allows not more than a one rule.